/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.util;

import java.beans.Introspector;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

/**
 * Miscellaneous class utility methods. Mainly for internal use within the
 * framework; consider
 * <a href="http://commons.apache.org/lang/" target="_blank">Apache Commons Lang</a>
 * for a more comprehensive suite of class utilities.
 *
 * @author Juergen Hoeller
 * @author Keith Donald
 * @author Rob Harrop
 * @author Sam Brannen
 * @since 1.1
 * @see TypeUtils
 * @see ReflectionUtils
 */
@SuppressWarnings("unchecked")
public abstract class ClassUtils {

   /** Suffix for array class names: "[]" */
   public static final String ARRAY_SUFFIX = "[]";

   /** Prefix for internal array class names: "[" */
   private static final String INTERNAL_ARRAY_PREFIX = "[";

   /** Prefix for internal non-primitive array class names: "[L" */
   private static final String NON_PRIMITIVE_ARRAY_PREFIX = "[L";

   /** The package separator character '.' */
   private static final char PACKAGE_SEPARATOR = '.';

   /** The inner class separator character '$' */
   private static final char INNER_CLASS_SEPARATOR = '$';

   /** The CGLIB class separator character "$$" */
   public static final String CGLIB_CLASS_SEPARATOR = "$$";

   /** The ".class" file suffix */
   public static final String CLASS_FILE_SUFFIX = ".class";


   /**
    * Map with primitive wrapper type as key and corresponding primitive
    * type as value, for example: Integer.class -> int.class.
    */
   private static final Map<Class<?>, Class<?>> primitiveWrapperTypeMap = new HashMap<Class<?>, Class<?>>(8);

   /**
    * Map with primitive type as key and corresponding wrapper
    * type as value, for example: int.class -> Integer.class.
    */
   private static final Map<Class<?>, Class<?>> primitiveTypeToWrapperMap = new HashMap<Class<?>, Class<?>>(8);

   /**
    * Map with primitive type name as key and corresponding primitive
    * type as value, for example: "int" -> "int.class".
    */
   private static final Map<String, Class<?>> primitiveTypeNameMap = new HashMap<String, Class<?>>(32);

   /**
    * Map with common "java.lang" class name as key and corresponding Class as value.
    * Primarily for efficient deserialization of remote invocations.
    */
   private static final Map<String, Class<?>> commonClassCache = new HashMap<String, Class<?>>(32);


   static {
      primitiveWrapperTypeMap.put(Boolean.class, boolean.class);
      primitiveWrapperTypeMap.put(Byte.class, byte.class);
      primitiveWrapperTypeMap.put(Character.class, char.class);
      primitiveWrapperTypeMap.put(Double.class, double.class);
      primitiveWrapperTypeMap.put(Float.class, float.class);
      primitiveWrapperTypeMap.put(Integer.class, int.class);
      primitiveWrapperTypeMap.put(Long.class, long.class);
      primitiveWrapperTypeMap.put(Short.class, short.class);

      for (Map.Entry<Class<?>, Class<?>> entry : primitiveWrapperTypeMap.entrySet()) {
         primitiveTypeToWrapperMap.put(entry.getValue(), entry.getKey());
         registerCommonClasses(entry.getKey());
      }

      Set<Class<?>> primitiveTypes = new HashSet<Class<?>>(32);
      primitiveTypes.addAll(primitiveWrapperTypeMap.values());
      primitiveTypes.addAll(Arrays.asList(
            boolean[].class, byte[].class, char[].class, double[].class,
            float[].class, int[].class, long[].class, short[].class));
      primitiveTypes.add(void.class);
      for (Class<?> primitiveType : primitiveTypes) {
         primitiveTypeNameMap.put(primitiveType.getName(), primitiveType);
      }

      registerCommonClasses(Boolean[].class, Byte[].class, Character[].class, Double[].class,
            Float[].class, Integer[].class, Long[].class, Short[].class);
      registerCommonClasses(Number.class, Number[].class, String.class, String[].class,
            Object.class, Object[].class, Class.class, Class[].class);
      registerCommonClasses(Throwable.class, Exception.class, RuntimeException.class,
            Error.class, StackTraceElement.class, StackTraceElement[].class);
   }


   /**
    * Register the given common classes with the ClassUtils cache.
    */
   private static void registerCommonClasses(Class<?>... commonClasses) {
      for (Class<?> clazz : commonClasses) {
         commonClassCache.put(clazz.getName(), clazz);
      }
   }

   /**
    * Return the default ClassLoader to use: typically the thread context
    * ClassLoader, if available; the ClassLoader that loaded the ClassUtils
    * class will be used as fallback.
    * <p>Call this method if you intend to use the thread context ClassLoader
    * in a scenario where you absolutely need a non-null ClassLoader reference:
    * for example, for class path resource loading (but not necessarily for
    * <code>Class.forName</code>, which accepts a <code>null</code> ClassLoader
    * reference as well).
    * @return the default ClassLoader (never <code>null</code>)
    * @see java.lang.Thread#getContextClassLoader()
    */
   public static ClassLoader getDefaultClassLoader() {
      ClassLoader cl = null;
      try {
         cl = Thread.currentThread().getContextClassLoader();
      }
      catch (Throwable ex) {
         // Cannot access thread context ClassLoader - falling back to system class loader...
      }
      if (cl == null) {
         // No thread context class loader -> use class loader of this class.
         cl = ClassUtils.class.getClassLoader();
      }
      return cl;
   }

   /**
    * Override the thread context ClassLoader with the environment's bean ClassLoader
    * if necessary, i.e. if the bean ClassLoader is not equivalent to the thread
    * context ClassLoader already.
    * @param classLoaderToUse the actual ClassLoader to use for the thread context
    * @return the original thread context ClassLoader, or <code>null</code> if not overridden
    */
   public static ClassLoader overrideThreadContextClassLoader(ClassLoader classLoaderToUse) {
      Thread currentThread = Thread.currentThread();
      ClassLoader threadContextClassLoader = currentThread.getContextClassLoader();
      if (classLoaderToUse != null && !classLoaderToUse.equals(threadContextClassLoader)) {
         currentThread.setContextClassLoader(classLoaderToUse);
         return threadContextClassLoader;
      }
      else {
         return null;
      }
   }

   /**
    * Replacement for <code>Class.forName()</code> that also returns Class instances
    * for primitives (like "int") and array class names (like "String[]").
    * <p>Always uses the default class loader: that is, preferably the thread context
    * class loader, or the ClassLoader that loaded the ClassUtils class as fallback.
    * @param name the name of the Class
    * @return Class instance for the supplied name
    * @throws ClassNotFoundException if the class was not found
    * @throws LinkageError if the class file could not be loaded
    * @see Class#forName(String, boolean, ClassLoader)
    * @see #getDefaultClassLoader()
    * @deprecated as of Spring 3.0, in favor of specifying a ClassLoader explicitly:
    * see {@link #forName(String, ClassLoader)}
    */
   @Deprecated
   public static Class<?> forName(String name) throws ClassNotFoundException, LinkageError {
      return forName(name, getDefaultClassLoader());
   }

   /**
    * Replacement for <code>Class.forName()</code> that also returns Class instances
    * for primitives (e.g."int") and array class names (e.g. "String[]").
    * Furthermore, it is also capable of resolving inner class names in Java source
    * style (e.g. "java.lang.Thread.State" instead of "java.lang.Thread$State").
    * @param name the name of the Class
    * @param classLoader the class loader to use
    * (may be <code>null</code>, which indicates the default class loader)
    * @return Class instance for the supplied name
    * @throws ClassNotFoundException if the class was not found
    * @throws LinkageError if the class file could not be loaded
    * @see Class#forName(String, boolean, ClassLoader)
    */
   public static Class<?> forName(String name, ClassLoader classLoader) throws ClassNotFoundException, LinkageError {
      Assert.notNull(name, "Name must not be null");

      Class<?> clazz = resolvePrimitiveClassName(name);
      if (clazz == null) {
         clazz = commonClassCache.get(name);
      }
      if (clazz != null) {
         return clazz;
      }

      // "java.lang.String[]" style arrays
      if (name.endsWith(ARRAY_SUFFIX)) {
         String elementClassName = name.substring(0, name.length() - ARRAY_SUFFIX.length());
         Class<?> elementClass = forName(elementClassName, classLoader);
         return Array.newInstance(elementClass, 0).getClass();
      }

      // "[Ljava.lang.String;" style arrays
      if (name.startsWith(NON_PRIMITIVE_ARRAY_PREFIX) && name.endsWith(";")) {
         String elementName = name.substring(NON_PRIMITIVE_ARRAY_PREFIX.length(), name.length() - 1);
         Class<?> elementClass = forName(elementName, classLoader);
         return Array.newInstance(elementClass, 0).getClass();
      }

      // "[[I" or "[[Ljava.lang.String;" style arrays
      if (name.startsWith(INTERNAL_ARRAY_PREFIX)) {
         String elementName = name.substring(INTERNAL_ARRAY_PREFIX.length());
         Class<?> elementClass = forName(elementName, classLoader);
         return Array.newInstance(elementClass, 0).getClass();
      }

      ClassLoader classLoaderToUse = classLoader;
      if (classLoaderToUse == null) {
         classLoaderToUse = getDefaultClassLoader();
      }
      try {
         return classLoaderToUse.loadClass(name);
      }
      catch (ClassNotFoundException ex) {
         int lastDotIndex = name.lastIndexOf('.');
         if (lastDotIndex != -1) {
            String innerClassName = name.substring(0, lastDotIndex) + '$' + name.substring(lastDotIndex + 1);
            try {
               return classLoaderToUse.loadClass(innerClassName);
            }
            catch (ClassNotFoundException ex2) {
               // swallow - let original exception get through
            }
         }
         throw ex;
      }
   }

   /**
    * Resolve the given class name into a Class instance. Supports
    * primitives (like "int") and array class names (like "String[]").
    * <p>This is effectively equivalent to the <code>forName</code>
    * method with the same arguments, with the only difference being
    * the exceptions thrown in case of class loading failure.
    * @param className the name of the Class
    * @param classLoader the class loader to use
    * (may be <code>null</code>, which indicates the default class loader)
    * @return Class instance for the supplied name
    * @throws IllegalArgumentException if the class name was not resolvable
    * (that is, the class could not be found or the class file could not be loaded)
    * @see #forName(String, ClassLoader)
    */
   public static Class<?> resolveClassName(String className, ClassLoader classLoader) throws IllegalArgumentException {
      try {
         return forName(className, classLoader);
      }
      catch (ClassNotFoundException ex) {
         throw new IllegalArgumentException("Cannot find class [" + className + "]", ex);
      }
      catch (LinkageError ex) {
         throw new IllegalArgumentException(
               "Error loading class [" + className + "]: problem with class file or dependent class.", ex);
      }
   }

   /**
    * Resolve the given class name as primitive class, if appropriate,
    * according to the JVM's naming rules for primitive classes.
    * <p>Also supports the JVM's internal class names for primitive arrays.
    * Does <i>not</i> support the "[]" suffix notation for primitive arrays;
    * this is only supported by {@link #forName(String, ClassLoader)}.
    * @param name the name of the potentially primitive class
    * @return the primitive class, or <code>null</code> if the name does not denote
    * a primitive class or primitive array class
    */
   public static Class<?> resolvePrimitiveClassName(String name) {
      Class<?> result = null;
      // Most class names will be quite long, considering that they
      // SHOULD sit in a package, so a length check is worthwhile.
      if (name != null && name.length() <= 8) {
         // Could be a primitive - likely.
         result = primitiveTypeNameMap.get(name);
      }
      return result;
   }

   /**
    * Determine whether the {@link Class} identified by the supplied name is present
    * and can be loaded. Will return <code>false</code> if either the class or
    * one of its dependencies is not present or cannot be loaded.
    * @param className the name of the class to check
    * @return whether the specified class is present
    * @deprecated as of Spring 2.5, in favor of {@link #isPresent(String, ClassLoader)}
    */
   @Deprecated
   public static boolean isPresent(String className) {
      return isPresent(className, getDefaultClassLoader());
   }

   /**
    * Determine whether the {@link Class} identified by the supplied name is present
    * and can be loaded. Will return <code>false</code> if either the class or
    * one of its dependencies is not present or cannot be loaded.
    * @param className the name of the class to check
    * @param classLoader the class loader to use
    * (may be <code>null</code>, which indicates the default class loader)
    * @return whether the specified class is present
    */
   public static boolean isPresent(String className, ClassLoader classLoader) {
      try {
         forName(className, classLoader);
         return true;
      }
      catch (Throwable ex) {
         // Class or one of its dependencies is not present...
         return false;
      }
   }

   /**
    * Return the user-defined class for the given instance: usually simply
    * the class of the given instance, but the original class in case of a
    * CGLIB-generated subclass.
    * @param instance the instance to check
    * @return the user-defined class
    */
   public static Class<?> getUserClass(Object instance) {
      Assert.notNull(instance, "Instance must not be null");
      return getUserClass(instance.getClass());
   }

   /**
    * Return the user-defined class for the given class: usually simply the given
    * class, but the original class in case of a CGLIB-generated subclass.
    * @param clazz the class to check
    * @return the user-defined class
    */
   public static Class<?> getUserClass(Class<?> clazz) {
      if (clazz != null && clazz.getName().contains(CGLIB_CLASS_SEPARATOR)) {
         Class<?> superClass = clazz.getSuperclass();
         if (superClass != null && !Object.class.equals(superClass)) {
            return superClass;
         }
      }
      return clazz;
   }

   /**
    * Check whether the given class is cache-safe in the given context,
    * i.e. whether it is loaded by the given ClassLoader or a parent of it.
    * @param clazz the class to analyze
    * @param classLoader the ClassLoader to potentially cache metadata in
    */
   public static boolean isCacheSafe(Class<?> clazz, ClassLoader classLoader) {
      Assert.notNull(clazz, "Class must not be null");
      ClassLoader target = clazz.getClassLoader();
      if (target == null) {
         return false;
      }
      ClassLoader cur = classLoader;
      if (cur == target) {
         return true;
      }
      while (cur != null) {
         cur = cur.getParent();
         if (cur == target) {
            return true;
         }
      }
      return false;
   }


   /**
    * Get the class name without the qualified package name.
    * @param className the className to get the short name for
    * @return the class name of the class without the package name
    * @throws IllegalArgumentException if the className is empty
    */
   public static String getShortName(String className) {
      Assert.hasLength(className, "Class name must not be empty");
      int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR);
      int nameEndIndex = className.indexOf(CGLIB_CLASS_SEPARATOR);
      if (nameEndIndex == -1) {
         nameEndIndex = className.length();
      }
      String shortName = className.substring(lastDotIndex + 1, nameEndIndex);
      shortName = shortName.replace(INNER_CLASS_SEPARATOR, PACKAGE_SEPARATOR);
      return shortName;
   }

   /**
    * Get the class name without the qualified package name.
    * @param clazz the class to get the short name for
    * @return the class name of the class without the package name
    */
   public static String getShortName(Class<?> clazz) {
      return getShortName(getQualifiedName(clazz));
   }

   /**
    * Return the short string name of a Java class in uncapitalized JavaBeans
    * property format. Strips the outer class name in case of an inner class.
    * @param clazz the class
    * @return the short name rendered in a standard JavaBeans property format
    * @see java.beans.Introspector#decapitalize(String)
    */
   public static String getShortNameAsProperty(Class<?> clazz) {
      String shortName = ClassUtils.getShortName(clazz);
      int dotIndex = shortName.lastIndexOf('.');
      shortName = (dotIndex != -1 ? shortName.substring(dotIndex + 1) : shortName);
      return Introspector.decapitalize(shortName);
   }

   /**
    * Determine the name of the class file, relative to the containing
    * package: e.g. "String.class"
    * @param clazz the class
    * @return the file name of the ".class" file
    */
   public static String getClassFileName(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      String className = clazz.getName();
      int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR);
      return className.substring(lastDotIndex + 1) + CLASS_FILE_SUFFIX;
   }

   /**
    * Determine the name of the package of the given class:
    * e.g. "java.lang" for the <code>java.lang.String</code> class.
    * @param clazz the class
    * @return the package name, or the empty String if the class
    * is defined in the default package
    */
   public static String getPackageName(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      String className = clazz.getName();
      int lastDotIndex = className.lastIndexOf(PACKAGE_SEPARATOR);
      return (lastDotIndex != -1 ? className.substring(0, lastDotIndex) : "");
   }

   /**
    * Return the qualified name of the given class: usually simply
    * the class name, but component type class name + "[]" for arrays.
    * @param clazz the class
    * @return the qualified name of the class
    */
   public static String getQualifiedName(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      if (clazz.isArray()) {
         return getQualifiedNameForArray(clazz);
      }
      else {
         return clazz.getName();
      }
   }

   /**
    * Build a nice qualified name for an array:
    * component type class name + "[]".
    * @param clazz the array class
    * @return a qualified name for the array class
    */
   private static String getQualifiedNameForArray(Class<?> clazz) {
      StringBuilder result = new StringBuilder();
      while (clazz.isArray()) {
         clazz = clazz.getComponentType();
         result.append(ClassUtils.ARRAY_SUFFIX);
      }
      result.insert(0, clazz.getName());
      return result.toString();
   }

   /**
    * Return the qualified name of the given method, consisting of
    * fully qualified interface/class name + "." + method name.
    * @param method the method
    * @return the qualified name of the method
    */
   public static String getQualifiedMethodName(Method method) {
      Assert.notNull(method, "Method must not be null");
      return method.getDeclaringClass().getName() + "." + method.getName();
   }

   /**
    * Return a descriptive name for the given object's type: usually simply
    * the class name, but component type class name + "[]" for arrays,
    * and an appended list of implemented interfaces for JDK proxies.
    * @param value the value to introspect
    * @return the qualified name of the class
    */
   public static String getDescriptiveType(Object value) {
      if (value == null) {
         return null;
      }
      Class<?> clazz = value.getClass();
      if (Proxy.isProxyClass(clazz)) {
         StringBuilder result = new StringBuilder(clazz.getName());
         result.append(" implementing ");
         Class<?>[] ifcs = clazz.getInterfaces();
         for (int i = 0; i < ifcs.length; i++) {
            result.append(ifcs[i].getName());
            if (i < ifcs.length - 1) {
               result.append(',');
            }
         }
         return result.toString();
      }
      else if (clazz.isArray()) {
         return getQualifiedNameForArray(clazz);
      }
      else {
         return clazz.getName();
      }
   }

   /**
    * Check whether the given class matches the user-specified type name.
    * @param clazz the class to check
    * @param typeName the type name to match
    */
   public static boolean matchesTypeName(Class<?> clazz, String typeName) {
      return (typeName != null &&
            (typeName.equals(clazz.getName()) || typeName.equals(clazz.getSimpleName()) ||
            (clazz.isArray() && typeName.equals(getQualifiedNameForArray(clazz)))));
   }


   /**
    * Determine whether the given class has a public constructor with the given signature.
    * <p>Essentially translates <code>NoSuchMethodException</code> to "false".
    * @param clazz   the clazz to analyze
    * @param paramTypes the parameter types of the method
    * @return whether the class has a corresponding constructor
    * @see java.lang.Class#getMethod
    */
   public static boolean hasConstructor(Class<?> clazz, Class<?>... paramTypes) {
      return (getConstructorIfAvailable(clazz, paramTypes) != null);
   }

   /**
    * Determine whether the given class has a public constructor with the given signature,
    * and return it if available (else return <code>null</code>).
    * <p>Essentially translates <code>NoSuchMethodException</code> to <code>null</code>.
    * @param clazz   the clazz to analyze
    * @param paramTypes the parameter types of the method
    * @return the constructor, or <code>null</code> if not found
    * @see java.lang.Class#getConstructor
    */
   public static <T> Constructor<T> getConstructorIfAvailable(Class<T> clazz, Class<?>... paramTypes) {
      Assert.notNull(clazz, "Class must not be null");
      try {
         return clazz.getConstructor(paramTypes);
      }
      catch (NoSuchMethodException ex) {
         return null;
      }
   }

   /**
    * Determine whether the given class has a method with the given signature.
    * <p>Essentially translates <code>NoSuchMethodException</code> to "false".
    * @param clazz   the clazz to analyze
    * @param methodName the name of the method
    * @param paramTypes the parameter types of the method
    * @return whether the class has a corresponding method
    * @see java.lang.Class#getMethod
    */
   public static boolean hasMethod(Class<?> clazz, String methodName, Class<?>... paramTypes) {
      return (getMethodIfAvailable(clazz, methodName, paramTypes) != null);
   }

   /**
    * Determine whether the given class has a method with the given signature,
    * and return it if available (else return <code>null</code>).
    * <p>Essentially translates <code>NoSuchMethodException</code> to <code>null</code>.
    * @param clazz   the clazz to analyze
    * @param methodName the name of the method
    * @param paramTypes the parameter types of the method
    * @return the method, or <code>null</code> if not found
    * @see java.lang.Class#getMethod
    */
   public static Method getMethodIfAvailable(Class<?> clazz, String methodName, Class<?>... paramTypes) {
      Assert.notNull(clazz, "Class must not be null");
      Assert.notNull(methodName, "Method name must not be null");
      try {
         return clazz.getMethod(methodName, paramTypes);
      }
      catch (NoSuchMethodException ex) {
         return null;
      }
   }

   /**
    * Return the number of methods with a given name (with any argument types),
    * for the given class and/or its superclasses. Includes non-public methods.
    * @param clazz   the clazz to check
    * @param methodName the name of the method
    * @return the number of methods with the given name
    */
   public static int getMethodCountForName(Class<?> clazz, String methodName) {
      Assert.notNull(clazz, "Class must not be null");
      Assert.notNull(methodName, "Method name must not be null");
      int count = 0;
      Method[] declaredMethods = clazz.getDeclaredMethods();
      for (Method method : declaredMethods) {
         if (methodName.equals(method.getName())) {
            count++;
         }
      }
      Class<?>[] ifcs = clazz.getInterfaces();
      for (Class<?> ifc : ifcs) {
         count += getMethodCountForName(ifc, methodName);
      }
      if (clazz.getSuperclass() != null) {
         count += getMethodCountForName(clazz.getSuperclass(), methodName);
      }
      return count;
   }

   /**
    * Does the given class or one of its superclasses at least have one or more
    * methods with the supplied name (with any argument types)?
    * Includes non-public methods.
    * @param clazz   the clazz to check
    * @param methodName the name of the method
    * @return whether there is at least one method with the given name
    */
   public static boolean hasAtLeastOneMethodWithName(Class<?> clazz, String methodName) {
      Assert.notNull(clazz, "Class must not be null");
      Assert.notNull(methodName, "Method name must not be null");
      Method[] declaredMethods = clazz.getDeclaredMethods();
      for (Method method : declaredMethods) {
         if (method.getName().equals(methodName)) {
            return true;
         }
      }
      Class<?>[] ifcs = clazz.getInterfaces();
      for (Class<?> ifc : ifcs) {
         if (hasAtLeastOneMethodWithName(ifc, methodName)) {
            return true;
         }
      }
      return (clazz.getSuperclass() != null && hasAtLeastOneMethodWithName(clazz.getSuperclass(), methodName));
   }

   /**
    * Given a method, which may come from an interface, and a target class used
    * in the current reflective invocation, find the corresponding target method
    * if there is one. E.g. the method may be <code>IFoo.bar()</code> and the
    * target class may be <code>DefaultFoo</code>. In this case, the method may be
    * <code>DefaultFoo.bar()</code>. This enables attributes on that method to be found.
    * <p><b>NOTE:</b> In contrast to {@link org.springframework.aop.support.AopUtils#getMostSpecificMethod},
    * this method does <i>not</i> resolve Java 5 bridge methods automatically.
    * Call {@link org.springframework.core.BridgeMethodResolver#findBridgedMethod}
    * if bridge method resolution is desirable (e.g. for obtaining metadata from
    * the original method definition).
    * @param method the method to be invoked, which may come from an interface
    * @param targetClass the target class for the current invocation.
    * May be <code>null</code> or may not even implement the method.
    * @return the specific target method, or the original method if the
    * <code>targetClass</code> doesn't implement it or is <code>null</code>
    */
   public static Method getMostSpecificMethod(Method method, Class<?> targetClass) {
      Method specificMethod = null;
      if (method != null && isOverridable(method, targetClass) &&
            targetClass != null && !targetClass.equals(method.getDeclaringClass())) {
         specificMethod = ReflectionUtils.findMethod(targetClass, method.getName(), method.getParameterTypes());
      }
      return (specificMethod != null ? specificMethod : method);
   }

   /**
    * Determine whether the given method is overridable in the given target class.
    * @param method the method to check
    * @param targetClass the target class to check against
    */
   private static boolean isOverridable(Method method, Class targetClass) {
      if (Modifier.isPrivate(method.getModifiers())) {
         return false;
      }
      if (Modifier.isPublic(method.getModifiers()) || Modifier.isProtected(method.getModifiers())) {
         return true;
      }
      return getPackageName(method.getDeclaringClass()).equals(getPackageName(targetClass));
   }

   /**
    * Return a public static method of a class.
    * @param methodName the static method name
    * @param clazz   the class which defines the method
    * @param args the parameter types to the method
    * @return the static method, or <code>null</code> if no static method was found
    * @throws IllegalArgumentException if the method name is blank or the clazz is null
    */
   public static Method getStaticMethod(Class<?> clazz, String methodName, Class<?>... args) {
      Assert.notNull(clazz, "Class must not be null");
      Assert.notNull(methodName, "Method name must not be null");
      try {
         Method method = clazz.getMethod(methodName, args);
         return Modifier.isStatic(method.getModifiers()) ? method : null;
      }
      catch (NoSuchMethodException ex) {
         return null;
      }
   }


   /**
    * Check if the given class represents a primitive wrapper,
    * i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.
    * @param clazz the class to check
    * @return whether the given class is a primitive wrapper class
    */
   public static boolean isPrimitiveWrapper(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      return primitiveWrapperTypeMap.containsKey(clazz);
   }

   /**
    * Check if the given class represents a primitive (i.e. boolean, byte,
    * char, short, int, long, float, or double) or a primitive wrapper
    * (i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double).
    * @param clazz the class to check
    * @return whether the given class is a primitive or primitive wrapper class
    */
   public static boolean isPrimitiveOrWrapper(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      return (clazz.isPrimitive() || isPrimitiveWrapper(clazz));
   }

   /**
    * Check if the given class represents an array of primitives,
    * i.e. boolean, byte, char, short, int, long, float, or double.
    * @param clazz the class to check
    * @return whether the given class is a primitive array class
    */
   public static boolean isPrimitiveArray(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      return (clazz.isArray() && clazz.getComponentType().isPrimitive());
   }

   /**
    * Check if the given class represents an array of primitive wrappers,
    * i.e. Boolean, Byte, Character, Short, Integer, Long, Float, or Double.
    * @param clazz the class to check
    * @return whether the given class is a primitive wrapper array class
    */
   public static boolean isPrimitiveWrapperArray(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      return (clazz.isArray() && isPrimitiveWrapper(clazz.getComponentType()));
   }

   /**
    * Resolve the given class if it is a primitive class,
    * returning the corresponding primitive wrapper type instead.
    * @param clazz the class to check
    * @return the original class, or a primitive wrapper for the original primitive type
    */
   public static Class<?> resolvePrimitiveIfNecessary(Class<?> clazz) {
      Assert.notNull(clazz, "Class must not be null");
      return (clazz.isPrimitive() && clazz != void.class? primitiveTypeToWrapperMap.get(clazz) : clazz);
   }

   /**
    * Check if the right-hand side type may be assigned to the left-hand side
    * type, assuming setting by reflection. Considers primitive wrapper
    * classes as assignable to the corresponding primitive types.
    * @param lhsType the target type
    * @param rhsType the value type that should be assigned to the target type
    * @return if the target type is assignable from the value type
    * @see TypeUtils#isAssignable
    */
   public static boolean isAssignable(Class<?> lhsType, Class<?> rhsType) {
      Assert.notNull(lhsType, "Left-hand side type must not be null");
      Assert.notNull(rhsType, "Right-hand side type must not be null");
      if (lhsType.isAssignableFrom(rhsType)) {
         return true;
      }
      if (lhsType.isPrimitive()) {
         Class resolvedPrimitive = primitiveWrapperTypeMap.get(rhsType);
         if (resolvedPrimitive != null && lhsType.equals(resolvedPrimitive)) {
            return true;
         }
      }
      else {
         Class resolvedWrapper = primitiveTypeToWrapperMap.get(rhsType);
         if (resolvedWrapper != null && lhsType.isAssignableFrom(resolvedWrapper)) {
            return true;
         }
      }
      return false;
   }

   /**
    * Determine if the given type is assignable from the given value,
    * assuming setting by reflection. Considers primitive wrapper classes
    * as assignable to the corresponding primitive types.
    * @param type the target type
    * @param value the value that should be assigned to the type
    * @return if the type is assignable from the value
    */
   public static boolean isAssignableValue(Class<?> type, Object value) {
      Assert.notNull(type, "Type must not be null");
      return (value != null ? isAssignable(type, value.getClass()) : !type.isPrimitive());
   }


   /**
    * Convert a "/"-based resource path to a "."-based fully qualified class name.
    * @param resourcePath the resource path pointing to a class
    * @return the corresponding fully qualified class name
    */
   public static String convertResourcePathToClassName(String resourcePath) {
      Assert.notNull(resourcePath, "Resource path must not be null");
      return resourcePath.replace('/', '.');
   }

   /**
    * Convert a "."-based fully qualified class name to a "/"-based resource path.
    * @param className the fully qualified class name
    * @return the corresponding resource path, pointing to the class
    */
   public static String convertClassNameToResourcePath(String className) {
      Assert.notNull(className, "Class name must not be null");
      return className.replace('.', '/');
   }

   /**
    * Return a path suitable for use with <code>ClassLoader.getResource</code>
    * (also suitable for use with <code>Class.getResource</code> by prepending a
    * slash ('/') to the return value). Built by taking the package of the specified
    * class file, converting all dots ('.') to slashes ('/'), adding a trailing slash
    * if necessary, and concatenating the specified resource name to this.
    * <br/>As such, this function may be used to build a path suitable for
    * loading a resource file that is in the same package as a class file,
    * although {@link org.springframework.core.io.ClassPathResource} is usually
    * even more convenient.
    * @param clazz   the Class whose package will be used as the base
    * @param resourceName the resource name to append. A leading slash is optional.
    * @return the built-up resource path
    * @see java.lang.ClassLoader#getResource
    * @see java.lang.Class#getResource
    */
   public static String addResourcePathToPackagePath(Class<?> clazz, String resourceName) {
      Assert.notNull(resourceName, "Resource name must not be null");
      if (!resourceName.startsWith("/")) {
         return classPackageAsResourcePath(clazz) + "/" + resourceName;
      }
      return classPackageAsResourcePath(clazz) + resourceName;
   }

   /**
    * Given an input class object, return a string which consists of the
    * class's package name as a pathname, i.e., all dots ('.') are replaced by
    * slashes ('/'). Neither a leading nor trailing slash is added. The result
    * could be concatenated with a slash and the name of a resource and fed
    * directly to <code>ClassLoader.getResource()</code>. For it to be fed to
    * <code>Class.getResource</code> instead, a leading slash would also have
    * to be prepended to the returned value.
    * @param clazz the input class. A <code>null</code> value or the default
    * (empty) package will result in an empty string ("") being returned.
    * @return a path which represents the package name
    * @see ClassLoader#getResource
    * @see Class#getResource
    */
   public static String classPackageAsResourcePath(Class<?> clazz) {
      if (clazz == null) {
         return "";
      }
      String className = clazz.getName();
      int packageEndIndex = className.lastIndexOf('.');
      if (packageEndIndex == -1) {
         return "";
      }
      String packageName = className.substring(0, packageEndIndex);
      return packageName.replace('.', '/');
   }

   /**
    * Build a String that consists of the names of the classes/interfaces
    * in the given array.
    * <p>Basically like <code>AbstractCollection.toString()</code>, but stripping
    * the "class "/"interface " prefix before every class name.
    * @param classes a Collection of Class objects (may be <code>null</code>)
    * @return a String of form "[com.foo.Bar, com.foo.Baz]"
    * @see java.util.AbstractCollection#toString()
    */
   public static String classNamesToString(Class... classes) {
      return classNamesToString(Arrays.asList(classes));
   }

   /**
    * Build a String that consists of the names of the classes/interfaces
    * in the given collection.
    * <p>Basically like <code>AbstractCollection.toString()</code>, but stripping
    * the "class "/"interface " prefix before every class name.
    * @param classes a Collection of Class objects (may be <code>null</code>)
    * @return a String of form "[com.foo.Bar, com.foo.Baz]"
    * @see java.util.AbstractCollection#toString()
    */
   public static String classNamesToString(Collection<Class> classes) {
      if (CollectionUtils.isEmpty(classes)) {
         return "[]";
      }
      StringBuilder sb = new StringBuilder("[");
      for (Iterator<Class> it = classes.iterator(); it.hasNext(); ) {
         Class clazz = it.next();
         sb.append(clazz.getName());
         if (it.hasNext()) {
            sb.append(", ");
         }
      }
      sb.append("]");
      return sb.toString();
   }


   /**
    * Return all interfaces that the given instance implements as array,
    * including ones implemented by superclasses.
    * @param instance the instance to analyze for interfaces
    * @return all interfaces that the given instance implements as array
    */
   public static Class[] getAllInterfaces(Object instance) {
      Assert.notNull(instance, "Instance must not be null");
      return getAllInterfacesForClass(instance.getClass());
   }

   /**
    * Return all interfaces that the given class implements as array,
    * including ones implemented by superclasses.
    * <p>If the class itself is an interface, it gets returned as sole interface.
    * @param clazz the class to analyze for interfaces
    * @return all interfaces that the given object implements as array
    */
   public static Class<?>[] getAllInterfacesForClass(Class<?> clazz) {
      return getAllInterfacesForClass(clazz, null);
   }

   /**
    * Return all interfaces that the given class implements as array,
    * including ones implemented by superclasses.
    * <p>If the class itself is an interface, it gets returned as sole interface.
    * @param clazz the class to analyze for interfaces
    * @param classLoader the ClassLoader that the interfaces need to be visible in
    * (may be <code>null</code> when accepting all declared interfaces)
    * @return all interfaces that the given object implements as array
    */
   public static Class<?>[] getAllInterfacesForClass(Class<?> clazz, ClassLoader classLoader) {
      Set<Class> ifcs = getAllInterfacesForClassAsSet(clazz, classLoader);
      return ifcs.toArray(new Class[ifcs.size()]);
   }

   /**
    * Return all interfaces that the given instance implements as Set,
    * including ones implemented by superclasses.
    * @param instance the instance to analyze for interfaces
    * @return all interfaces that the given instance implements as Set
    */
   public static Set<Class> getAllInterfacesAsSet(Object instance) {
      Assert.notNull(instance, "Instance must not be null");
      return getAllInterfacesForClassAsSet(instance.getClass());
   }

   /**
    * Return all interfaces that the given class implements as Set,
    * including ones implemented by superclasses.
    * <p>If the class itself is an interface, it gets returned as sole interface.
    * @param clazz the class to analyze for interfaces
    * @return all interfaces that the given object implements as Set
    */
   public static Set<Class> getAllInterfacesForClassAsSet(Class clazz) {
      return getAllInterfacesForClassAsSet(clazz, null);
   }

   /**
    * Return all interfaces that the given class implements as Set,
    * including ones implemented by superclasses.
    * <p>If the class itself is an interface, it gets returned as sole interface.
    * @param clazz the class to analyze for interfaces
    * @param classLoader the ClassLoader that the interfaces need to be visible in
    * (may be <code>null</code> when accepting all declared interfaces)
    * @return all interfaces that the given object implements as Set
    */
   public static Set<Class> getAllInterfacesForClassAsSet(Class clazz, ClassLoader classLoader) {
      Assert.notNull(clazz, "Class must not be null");
      if (clazz.isInterface() && isVisible(clazz, classLoader)) {
         return Collections.singleton(clazz);
      }
      Set<Class> interfaces = new LinkedHashSet<Class>();
      while (clazz != null) {
         Class<?>[] ifcs = clazz.getInterfaces();
         for (Class<?> ifc : ifcs) {
            interfaces.addAll(getAllInterfacesForClassAsSet(ifc, classLoader));
         }
         clazz = clazz.getSuperclass();
      }
      return interfaces;
   }

   /**
    * Create a composite interface Class for the given interfaces,
    * implementing the given interfaces in one single Class.
    * <p>This implementation builds a JDK proxy class for the given interfaces.
    * @param interfaces the interfaces to merge
    * @param classLoader the ClassLoader to create the composite Class in
    * @return the merged interface as Class
    * @see java.lang.reflect.Proxy#getProxyClass
    */
   public static Class<?> createCompositeInterface(Class<?>[] interfaces, ClassLoader classLoader) {
      Assert.notEmpty(interfaces, "Interfaces must not be empty");
      Assert.notNull(classLoader, "ClassLoader must not be null");
      return Proxy.getProxyClass(classLoader, interfaces);
   }

   /**
    * Check whether the given class is visible in the given ClassLoader.
    * @param clazz the class to check (typically an interface)
    * @param classLoader the ClassLoader to check against (may be <code>null</code>,
    * in which case this method will always return <code>true</code>)
    */
   public static boolean isVisible(Class<?> clazz, ClassLoader classLoader) {
      if (classLoader == null) {
         return true;
      }
      try {
         Class<?> actualClass = classLoader.loadClass(clazz.getName());
         return (clazz == actualClass);
         // Else: different interface class found...
      }
      catch (ClassNotFoundException ex) {
         // No interface class found...
         return false;
      }
   }

}
